Single communication channel between a contactless frontend device and a transceiver device

ABSTRACT

Method for exchanging data between an NFC device ( 10 ) and a transceiver device ( 20 ) via a single communication channel ( 30 ), comprising the steps:—extracting a clock for the data exchange on the communication channel ( 30 ) from an external RF field ( 50 ); and—coding of the data via symbols, wherein the symbols comprise status information relating to simultaneous accesses of contactless card functionalities ( 21, 22, 23 ) on the transceiver ( 20 ) to the single communication channel ( 30 ).

FIELD OF THE INVENTION

The invention relates to a method and a device for exchanging databetween a contactless frontend device and a transceiver device.

BACKGROUND OF THE INVENTION

Nowadays, many smart cards according to the standard ISO/IEC 14443 andISO/IEC 18092 are used. These smart cards can e.g. be formed as a SIM(Subscriber Identity Module) with integrated mobile phone functionality.Furthermore, the smart cards can also be formed as a SAM (Secure AccessModule) which is a dedicated microprocessing unit for authenticatingprocedures.

In standard applications, the smart cards are directly connected with anantenna via analog signal lines. However, for additional applications ofsmart cards, particularly when they are employed in SIM modules, itwould also be desirable to directly connect existing types of smartcards with near field communication (NFC) devices without the need toprovide separate antennas for both the smart card and the NFC device. Inorder to connect smart cards and NFC devices with each other, acommunication channel is foreseen for such purpose.

From standard ECMA-373 a near field communication wired interface(NFC-WI) with two wires is known. Furthermore, from ETSI documentSCPt060577 there is known a single wire interface between a smart cardand an NFC frontend device.

OBJECT AND SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved singlecommunication channel between a contactless frontend device and a smartcard acting as a secure transceiver device.

According to the invention there is provided a method for exchangingdata between a contactless frontend device and a transceiver device viaa single communication channel, comprising the steps: extracting a clockfor the data exchange on the communication channel from an externalRF-field, and coding of the data via symbols, wherein the symbolscomprise status information relating to simultaneous accesses ofcontactless card functionalities on the transceiver to the singlecommunication channel.

In this way, simultaneous accesses of contactless card functionalitieson the smart card are supported by the inventive method. Due to the factthat a clock period for an “internal” data communication between thecontactless frontend device and the smart card is extracted from theexternal RF field, a well defined real-time inventory procedure beinginitiated by the external reader is thus supported. In a preferredembodiment of the method according to the invention, a framing of thedata on the single communication channel is bit-oriented. Thus, themethod is well suited to support real time and anticollisionrequirements of ISO/IEC 14443 Type A and B, ISO/IEC 18092 or ISO/IEC15693.

According to the invention, there is further provided a singlecommunication channel for an exchange of data between a contactlessfrontend device and a transceiver device, wherein the data are coded viasymbols, wherein the symbols comprise status information relating tosimultaneous accesses of contactless card functionalities on thetransceiver device to the single communication channel. By means of theinventive single communication channel, advantageously, a multiplicityof contactless card functionalities can simultaneously access the singlecommunication channel without disturbing a well defined information flowbetween the external reader and a dedicated one out of the emulated cardfunctionalities.

The aspects defined above and further aspects of the invention areapparent from an exemplary embodiment to be described and explained withreference to this exemplary embodiment hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained now in greater detail withreference to the following figures:

FIG. 1 shows in principle a block diagram of an RFID communicationsystem with a contactless frontend device, a transceiver device and asingle communication channel arranged in between.

FIG. 2 shows in principle a framing of data and status information beingexchanged on the single communication channel.

DESCRIPTION OF EMBODIMENTS

FIG. 1 shows in principle a block diagram of an RFID communicationsystem 100 with a contactless frontend device 10. The contactlessfrontend device 10 can e.g. be formed as a near field communication(NFC) frontend device being galvanically connected to a contactlessterminal, e.g. an antenna 40. By means of the antenna 40, the RFIDcommunication system 100 is able to communicate with an external reader(not shown) via an external RF-field 50. Via the antenna 40 thecontactless frontend device 10 supports a wireless communication beingcompliant with ISO/IEC 14443 or ISO/IEC 15693 or ISO/IEC 18092. Thecontactless frontend device 10 is connected to a smart card 20 (e.g.formed as a SIM card) via a single communication channel 30. Preferably,the single communication channel 30 is formed by a single wire. However,in principle it is also possible that the single communication channel30 is formed as a wireless communication channel between the contactlessfrontend device 10 and the smart card 20. The smart card 20 actspreferably as a secure transceiving unit, which means that it sends andtransmits data to the contactless frontend device 10 via the singlecommumnication channel 30 in a secure manner with authenticatingfunctionality. Inside the smart card 20 there are arrangeable andexecuteable a muliplicity of secure emulated contactless cardfunctionalities 21, 22, 23. These functionalities 21, 22, 23 can e.g. beformed as reader and/or payment and/or authenticating functionalities.However, though not explicitely shown, also additional contactless cardfunctionalities are possible to be arrangeable and executeable on thesmart card 20. Furthermore, the smart card 20 can also be formed as asecure access module (SAM) with integrated authenticatingfunctionalities.

A high speed data connection 60 (e.g. via the USB protocol) is arrangedbetween the smart card 20 and a baseband IC (not shown) of the RFIDcommunication system 100 and is foreseen to exchange high speed databetween the smart card 20 and the baseband IC. Due to hardwarerequirements of said high speed connection 60, an availability ofhardware resources on the smart card 20 for the connection to thecontactless frontend device 10 may be limited. Therefore, it isdesirable to provide an improved single communication channel betweenthe contactless frontend device 10 and the smart card 20.

According to the invention, there is foreseen a single communicationchannel 30 with improved features over conventional single communicationchannels. For example, a handling of a conventional RF-communicationprotocol (which handles, amongst others, a coding and framing of data onthe RF field 50, a handling of synchronization-bits, an amount of databits inside data frames, cyclic-redundancy-checks (CRC) and so on)between the external reader and the transceiver 20 is exclusively andcompletely handled by the smart card 20, preferably inside the smartcard 20. Hence, security relevant portions of the RF-communicationprotocol are handled inside the smart card 20, thus hampering anyharmful spy-attacks to the RFID communication system 100. In this way,it is advantageously impossible to decouple a handling of the inventoryprocedure between the contactless frontend device 10 and the smart card20. An additional protocol according to the invention handles the dataexchange on the single communication channel 30 and is performed both bythe contactless frontend device 10 and the transceicer 20. For the sakeof unambiguousness, said protocol is referenced with CP-protocol(“Common protocol”) hereinafter. The CP-protocol has a transparentbehaviour for the data of the RF-protocol and has two main challenges.Firstly, it hands over data from the RF-protocol for a data transmissionon the single communication channel 30 in a transparent or mirroringbehaviour. Furthermore, the CP-protocol handles an exchange of statusinformation between the contactless frontend device 10 and the smartcard 20.

Preferably, the single communciation channel 30 offers half duplexperformance. Advantageously, said half duplex performance accommodatesrequirements of the contactless frontend devide 10 and reduces hardwarecomplexities. Therefore, it supports a cost-saving realization of thesingle communication channel 30. Furthermore, data on the singlecommunication channel 30 are coded via electrical voltage levels. Tothis end, the contactless frontend device 10 is able to pull anelectrical signal level of the single communication channel 30 up to alogical “HIGH” level. In equivalence thereto, the smart card 20 is ableto pull a signal condition on the commmunication channel to a logical“LOW” level. In other words, the logical “HIGH” level is always drivenby the contactless frontend device 10, whereas the logical “LOW” levelis always driven by the smart card 20.

In more detail, during sending clock/direction information and/or datato the contactless frontend device 10, the contactless frontend device10 drives both the logical “HIGH” and the logical “LOW” level strong.During reception of data from the smart card 20, the frontend device 10drives a weak “HIGH” level. In correspondence thereto, the smart card 20drives the “LOW” level strong. Moreover, the “HIGH” level is neverdriven by the smart card 20. Thus, advantageously, a multiplicity ofcard functionalities 21, 22, 23 on the smart cards 20 can simultaneouslyaccess the single communication channel 30 by maintaining well definedphysical and logical conditions on the single communication channel 30.Due to the fact that signal conditions on the single communicationchannel 30 are represented by electrical voltages, advantageously,standard digital I/O pads may be used on the smart card 20 for agalvanical connection to the single communication channel 30.

FIG. 2 shows in principle an exemplary implementation of a data frame FRbeing transmitted on the single communication channel 30 by means of theCP-protocol. A fundamental time base t_(B) of the data frame FR isextracted from the external RF field 50 by the contactless frontenddevice 10. To this end, the contactless frontend device 10 calculatesthe time base t_(B) from received signals from the external reader (notshown) via calculation algorithms. The time base t_(B) has preferably alength between 60 nanoseconds and 2400 nanoseconds. Thus, a data rate onthe single communication channel 30 is in accordance with a data rate onthe external RF field 50. Resulting therefrom, advantageously, any kindof data buffering inside the contactless frontend device 10 or insidethe smart card 20 is superfluous, as there is no difference between thementioned data rates. Furthermore, a clock oscillator 25 can be arrangedon the smart card 20 and is foreseen to calculate the data rate from thetime base t_(B) on the single communication channel 30. For thiscalculation, technical requirements to the clock oscillator 25 can below, so that no high-qualitative clock oscillators 25 are necessary tobe implemented in the smart card 20.

A clock period CLK, on which the data transmissison rate inside the dataframe FR is based, has a length of 3×t_(B) (duty cycle ⅔). The length ofthe time base t_(B) is extracted from the external RF field 50, asmentioned above. Furthermore, the data frame FR comprises a directionbit DIR, which defines a direction of a data transmission between thecontactless frontend device 10 and the smart card 20. In a case, thatthe direction bit DIR is “LOW”, data are transmitted from thecontactless frontend device 10 to the smart card 20. In a case, that thedirection bit DIR is “HIGH”, data are transmitted from the smart card 20to the contactless frontend device 10. Due to the fact, that the clockCLK for the single communication channel 30 is extracted from theexternal RF field 50, a separate clock oscillator inside the contactlessfrontend device 10 is advantageously superfluous. However, it should bementioned, that nevertheless any kind of clock oscillator may beforeseen to be implemented in the contactless frontend device 10. Thedate frame FR further comprises six so called “code units” CU. The codeunits have a numbering from 1 to 6 (CU1 to CU6). As can be seen fromFIG. 2, CU6 operates as a most significant bit (MSB) and CU1 operates asa least significant bit (LSB) inside a data portion DATA of the dataframe FR. The direction bit DIR and each of the code units CU1 to CU6have preferably a length of 3×t_(B).

A meaning of a coding of the code units CU1 to CU6, bits bit1, bit2,bit3 of the data frame FR and status information which are all handledby the inventive CP-protocol are illustrated in more detail with respectto the following table:

TABLE 1 CU 6 MSB CU 5 CU 4 CU 3 CU 2 CU 1 LSB bit 1 bit 2 bit 3 Symbolbit 1 bit 2 bit 3 11 No data No data No data Frame = Status Information10 “0” “0” “0” 01 “1” “1” “1” 00 Collision Collision CollisionTable 1 shows an exemplary mapping of bits (code units, respectively)inside the data frame FR to digital symbols. As can be seen, bits insidethe data frame FR are named as bit 1, bit 2, bit 3 and are formed as acombination two code units. A mapping between the digital symbols andthe bits 1, 2 and 3 is as follows: CU6 is the most significant singlebit (MSB), CU1 is the least significant bit (LSB) inside a data portionDATA of the data frame FR. CU6 (MSB) and CU5 together form bit 1, CU4and CU3 together form bit 2 and CU2 and CU1 (LSB) together form bit 3.

In case, that for bit 1 the digital symbol “11” is transmitted on thesingle communication channel 30, this means that no data are to betransmitted in the subsequent data frame FR. Instead, in this case theremay be sent numerous status information which are formed of the bits 2and 3. For example, an initiation of a speed change on the singlecommunication channel 30 can be implemented in this way. Furthermore,also activation/deactivation or idle commands can be transmitted fromthe contactless frontend device 10 to the smart card 20 or vice versa.In this way, a total amount of 16 different status messages areimplementable by the possible 16 states of a combination of bits 2 and3.

Furthermore, in case that for any of the bits 1, 2, or 3 the digitalsymbol “10” is assigned, this means a transmission of digital data “0”.Furthermore, in case that to any of the bits 1, 2, or 3 the digitalsymbol “01” is assigned, this means a transmission of digital data “1”.In a case that the external reader starts an inventory procedure of thecontactless card functionalities 21, 22, 23 on the smart card 20, atleast two or more of the contactless card funtionalities may respondsimultaneously to the inventory procedure. This results in an assignmentof the digital symbol “00” to any of the bits 1, 2 or 3 and atransmission of this digital symbol on the single communication channel30. If any of the bits 1, 2 or 3 shows a content of digital “00”, thisfact indicates to the external reader, that at least two contactlesscard functionalities on the smart card 20 had tried to access the singlecommunication channel 30 simultaneously.

Hence, a state of “collision” is transmitted on the single communicationchannel 30. From this information, advantageously, the external readermay repeat or cancel its inventory procedure, thus obtaining a timelywell defined response behaviour of all of the inventoried secureemulated contactless card functionalities 21, 22, 23 on the smart card20. Therefore, by means of the single communication channel 30 accordingto the invention, a response behaviour of numerous contactless cardfunctionalities to an inventory procedure of an external reader can bewell structured. Summarizing, the method according to the presentinvention allows an emulation of more than one contactless cardfunctionality 21, 22, 23 on the smart card 20. Further, also more than asingle smart card 20 may be connected to the single communicationchannel 30, thus also allowing an emulation of more than one contactlesscard functionality.

As can be easily seen from FIG. 2 and table 1, the arrangement of bitsto be exchanged on the single communication channel 30 is bit oriented.Resulting therefrom, together with the fact that the data rate on thesingle communication channel 30 matches exactly the data rate in theexternal RF field 50, the method according to the invention supportsreal time- and/or anticollision requirements of ISO/IEC 14443. Further,the single communication channel 30 according to the invention providesa simultaneous transmission of clock, data and control informationbetween the contactless frontend device 10 and the smart card 20. Thisprovides the quality that the clock CLK is extracted from the externalRF field 50, thus supporting an avoidance of any kind of data congestionin the RFID communication system 100. Furthermore, by use of theinvention any conversions between the conventional RF-protocol and theCP-protocol are superfluous. This saves an overhead of protocol handlingand thus further supports the fulfilment of the above mentioned realtime- and anticollision requirements. As a result, the external reader,advantageously, does not realize an existence of the contactlessfrontend device 10 and is able to perform a “direct” communicationprocedure with the smart card 20.

It should further be observed, that, although the present invention hasbeen illustrated by an embodiment which is an implementation accordingto ISO/IEC 14443 or ISO/IEC 18092 or ISO/IEC 15693, the presentinvention is not limited to these standards, but is also applicable toany RFID communication systems with comparable timing requirements.

Finally, it should be noted that the above-mentioned embodimentsillustrate rather than limit the invention, and that those skilled inthe art will be capable of designing many alternative embodimentswithout departing from the scope of the invention as defined by theappended claims. In the claims, any reference signs placed inparentheses shall not be construed as limiting the claims. The word“comprising” and “comprises”, and the like, does not exclude thepresence of elements or steps other than those listed in any claim orthe specification as a whole. The singular reference of an element doesnot exclude the plural reference of such elements and vice-versa. In adevice claim enumerating several means, several of these means may beembodied by one and the same item of software or hardware. The mere factthat certain measures are recited in mutually different dependent claimsdoes not indicate that a combination of these measures cannot be used toadvantage.

1. A method for exchanging data between a contactless frontend deviceand a transceiver device via a single communication channel, comprisingthe steps: extracting a clock (CLK) for the data exchange on the singlecommunication channel from an external RF-field; and coding of the datavia symbols, wherein the symbols comprise status information relating tosimultaneous accesses of contactless card functionalities on thetransceiver to the single communication channel.
 2. The method accordingto claim 1, wherein the data on the single communication channel arecoded via electrical voltages.
 3. The method according to claim 2,wherein a framing of the data on the single communication channel isbit-oriented.
 4. Method according to claim 3, wherein the exchange ofthe data on the single communication channel is executable inhalf-duplex. 5 The method according to claim 1, wherein anRF-communication protocol is executable completely by the transceiver,and wherein a protocol for the single communication channel isexecutable by the contactless frontend device and by the transceiver. 6.The method according to claim 5, wherein the method is executable for aplurality of the transceivers being connected to the singlecommunication channel.
 7. A single communication channel for an exchangeof data between a contactless frontend device and a transceiver device,wherein the data are coded via symbols, wherein the symbols comprisestatus information relating to simultaneous accesses of contactless cardfunctionalities on the transceiver device to the single communicationchannel.
 8. The single communication channel according to claim 7,wherein the single communication channel is formed as a single wire. 9.The single communication channel according to claim 8, wherein the dataon the single communication channel are coded via electrical voltages.10. The single communication channel according to claim 9, wherein theexchange of the data is executable in half duplex.
 11. The singlecommunication channel according to claim 10, wherein an RF-communicationprotocol is executable completely by the transceiver, and wherein aprotocol for the single communication channel is executable by thecontactless frontend device and by the transceiver.
 12. The singlecommunication channel according to claim 11, wherein the method isexecutable for a plurality of the transceivers being connected to thesingle communication channel.
 13. An RFID communication system,comprising a contactless frontend device, a transceiver device and asingle communication channel, wherein the single communication channelis connected both to the contactless frontend device and to thetransceiver device.